Sen. Tim Johnson was one of the last remaining holdouts in the Senate among Democrats on marriage equality but announced today that he's "evolved."

Johnson is retiring at the end of this term as South Dakota's senator, and his son Brendan is considered a possible candidate to replace him in 2014.

"After lengthy consideration, my views have evolved sufficiently to support marriage equality legislation," he said in a statement released today. "This position doesn't require any religious denomination to alter any of its tenets; it simply forbids government from discrimination regarding who can marry whom."

South Dakota's other senator, Republican John Thune, remains opposed to marriage equality.

This means there are now 54 votes — including two Republicans — in favor of marriage equality in the Senate. Only three Democrats remain opposed — Sen. Mark Pryor of Arkansas, Sen. Joe Manchin of West Virginia and Sen. Mary Landrieu of Louisiana.

The latest answer from Landrieu, who is up for reelection next year, sends a conflicting message about where she stands. While Landrieu said her personal view is that "people should love who they love and marry who they want to marry," she is committed to representing her state's view instead. "My state has a very strong constitutional amendment not only against gay marriage but against gay partnerships. So I'm looking at the people of Louisiana trying to represent their interests," she told CNN on Friday.

Pryor is also up for reelection in 2014 in a state not considered favorable for Democrats and said on Friday that he's now "undecided" on marriage equality.

Manchin won reelection to full term last year but is best remembered as the senator who shot a gun in a campaign ad to show voters how different he is from your typical Democrat. "I believe that a marriage is a union between one man and one woman," Manchin said in a statement to Talking Points Memo on Tuesday. "My beliefs are guided by my faith, and I support the Defense of Marriage Act."